Product marked with Free / Low Shipping included a free shipping credit to offset the actual shipping cost. Whether it is free shipping depends on the combination and quantity of the products you purchase.

Just add a product marked with "free/low shipping" to the shipping cost to estimate the shipping cost. You can try to add more different products marked with "free shipping" to offset the shipping cost.

No argument on shipping cost you have paid after you purchase. Thank you for your understanding.